The present invention relates to technique for reproducing or recording data from/to an optical disc.
For a medium for recording information, a magnetic tape and a disc can be given.
For the magnetic tape, a magnetic tape on which analog signals are serially recorded for a long time such as one used in VTR is well-known.
In the meantime, for the disc, an optical disc on which digital information is recorded can be given, it is used for an external storage of a computer and an apparatus for recording or reproducing an aural signal or a picture signal to/from an optical disc has been manufactured. As information can be recorded or reproduced to/from an optical disc at random, compared with a magnetic tape on which information is serially recorded, the optical disc has a merit that access to information is promptly enabled.
The above-mentioned optical disc has various types such as a compact disc (CD) and a digital video disc (a digital versatile disc) (DVD), for CD, a compact disc read only memory (CD-ROM), a compact disc-recordable (CD-R) and CD-rewritable (CD-RW) are known and for DVD, there are single-layer DVD-read only memory (DVD-ROM), dual-layer DVD-ROM, DVD-recordable (DVD-R), DVD-random access memory version 1.0 (DVD-RAM1) DVD-RAM2, DVDxe2x88x92RW and DVD+ReWritable (DVD+RW) (a rewritable DVD standard settled by Sony Corporation, Philips Electronics, Hewlett Packard, Mitsubishi Chemical Industries, Ltd., Ricoh Co., Ltd. and Yamaha Motor Co., Ltd. and called Phase-Change ReWritable).
As some of these plural types of optical discs are different in a method of recording and reproducing information, each optical disc is required to be switched. Therefore, the type of an optical disc to/from which information is to be recorded or reproduced is required to be discriminated.
For reference examples of discriminating an optical disc, Japanese unexamined publication No. H11-306650, No. H10-334574, No. H9-44982 and No. H8-249801 can be given.
However, in the above-mentioned reference examples, technique for discriminating a disc the reflected light quantity, the distance to a recording face and the recording track pitch of which are small is not referred and for a discriminating method, realizing means is not disclosed.
For example, DVD-RAM which is DVD-RAM1 or DVD-RAM2 and DVDRW which is DVDxe2x88x92RW or DVD+RW are substantially equal in reflected light quantity and distance to a recording face.
For recording track pitch, each track pitch of DVD-RAM and DVDRW is also smaller than each track pitch of CD and DVD.
Therefore, for a method of discriminating DVD-RAM and DVDRW, a new discriminating method is required to be discussed in addition to a method based upon reflected light quantity, distance to a recording face and recording track pitch.
Japanese published unexamined patent publication No. H11-306650 discloses a method of synthetically discriminating a disc after beams are once necessarily emitted from both laser beam sources for CD and for DVD and reflected signals based upon reflected light by both laser beam sources for CD and for DVD, a focus error signal and a tracking error signal are all acquired, however, the process is complex.
The object of the invention is to solve the above-mentioned problems and to provide disc discriminating method and apparatus by which an optical disc can be easily discriminated.
To achieve the object of the invention, a disc discriminating method according to the invention includes a step for discriminating the type of an optical disc installed in an optical disc unit based upon the reflectance, a step for discriminating the type of the optical disc based upon the time of a reflected signal from the surface of the optical disc and the time of the reflected signal from the recording face and a step for discriminating the type of the optical disc based upon a tracking error signal acquired from the optical disc.
Further, in addition to the above-mentioned steps, a step for determining the number of recording layers of an optical disc based upon a focus error signal acquired from the recording face of the optical disc and/or a step for discriminating the type of the optical disc depending upon the amplitude values of the reflected lights of laser beams from different lasers may be also together or selectively added.
First, in the step for discriminating the type of the optical disc based upon a tracking error signal acquired from the optical disc, the amplitude of a push-pull tracking error signal is acquired in a state in which focus servo is executed, is compared with a predetermined value and the type of the optical disc is discriminated.
That is, some optical discs are different in the sensitivity of a push-pull tracking error signal and as the difference in the sensitivity makes difference in the amplitude value of the tracking error signal, an optical disc can be discriminated based upon the difference.
For example, it is known that when DVD-RAM which is DVD-RAM1 or DVD-RAM2 and DVDRW which is DVDxe2x88x92RW or DVD+RW are compared, DVD-RAM is larger than DVDRW in the amplitude value of the tracking error signal.
Therefore, in case the amplitude of a tracking error signal is larger than a predetermined value, an optical disc is judged as DVD-RAM and in case the amplitude is smaller than the predetermined value, the optical disc can be judged as DVDRW.
Next, in the step for discriminating the type of an optical disc based upon the reflectance of the optical disc, the type of the optical disc is discriminated by determining whether the amplitude of a focus error signal acquired from the optical disc is larger than a predetermined value or not.
Generally, it is known that when optical discs are sorted in the order of higher reflectance, they are sorted in the order of CD, single-layer DVD (however, as difference in reflectance between CD and single-layer DVD is small, it may be also described that they are equal in reflectance), CD-R, dual-layer DVD, CD-RW, DVDRW (DVDxe2x88x92RW or DVD+RW) and DVD-RAM (however, as difference in reflectance among CD-RW, DVD-RAM and DVDRW is small, it may be also described that they are equal in reflectance).
Therefore, the type of an optical disc can be discriminated by presetting the amplitude values for comparison of focus error signals from these optical discs and comparing the preset amplitude value and the amplitude of a focus error signal from each optical disc.
For example, in the step for discriminating the reflectance of an optical disc, CD and single-layer DVD can be discriminated as an optical disc the reflectance of which is large, and CD-RW, DVDRW and DVD-RAM can be discriminated as an optical disc the reflectance of which is small.
In the step for discriminating the type of an optical disc, as there is difference between time until a reflected signal from the surface of the optical disc is acquired and time until a reflected signal from the recording face of the optical disc is acquired, the type of the optical disc is discriminated based upon the difference between the times.
For example, for CD and DVD, it is generally known that CD is larger in the difference between the times.
Therefore, for CD and DVD, in case the difference between the times is longer than predetermined time, the optical disc can be judged as CD and in case the difference is shorter, the optical disc can be judged as DVD.
In the step for determining the number of recording layers of an optical disc based upon a focus error signal acquired from the recording face of the optical disc, the number of focus error signals acquired when an optical pickup provided to the optical disc unit is brought close to the installed optical disc or is separated from it is counted.
For example, DVD the number of focus error signals acquired from the recording face of which is one can be determined as single-layer DVD and DVD the number of focus error signals acquired from the recording faces of which is two can be determined as dual-layer DVD.
In the step for discriminating the type of an optical disc depending upon difference in the amplitude values of the reflected lights of laser beams from different lasers, the type of the optical disc is discriminated by switching a first laser and a second laser and measuring difference between reflected signals or counting the number of reflected signals.
Generally, it is known that difference in the amplitude value of the reflected light of the radiated laser beam is made depending upon an optical disc on which a laser beam is radiated.
For example, in case a laser beam for DVD is radiated on CD-R, no reflected light the amplitude of which is large is acquired.
Therefore, for CD and CD-R, in case the amplitude value of a focus error signal by a CD laser is larger than that of a focus error signal by a DVD laser when CD lasers beam and DVD laser beams are radiated, the corresponding optical disc can be judged as CD-R. Of course, a predetermined value is set beforehand, the corresponding optical disc for which two focus error signals having the amplitude larger than the predetermined value are acquired may be also judged as CD and the corresponding optical disc for which only one focus error signal is acquired may be also judged as CD-R.
A method of radiating different laser beams is not limited to the above-mentioned method and may be also a method of acquiring a focus error signal, approaching the optical pickup of the optical disc unit toward an optical disc using either of the first laser or the second laser, acquiring a focus error signal, separating the optical pickup from the optical disc using the other laser, comparing the amplitude values of the acquired focus error signals and counting the numbers.
For a method of discriminating DVD-RAM and DVDRW after the corresponding optical disc is determined as either of DVD-RAM or DVDRW, the following disc discriminating method is also useful.
First, suppose that a focus servo and a tracking servo are operated under setting for DVD-RAM in the optical disc unit. Next, it can be determined based upon a frequency of an acquired wobble signal whether the corresponding optical disc is DVD-RAM or DVDRW.
Generally, a standard determines so that frequencies of a wobble signal are different between DVD-RAM and DVDRW.
Therefore, in the above-mentioned case, if the frequency of an acquired wobble signal indicates DVD-RAM, the corresponding optical disc can be determined as DVD-RAM.
Of course, a method according to the invention is not limited to the method of acquiring a wobble signal after DVD-RAM is set as described above and for example, after DVD-RAM is set, information on an optical disc can be reduced. Or an optical disc may be also judged as DVD-RAM if address information is acquired from an optical disc.
Therefore, discrimination in case an optical disc is DVDRW in the above-mentioned case is different from may be also performed based upon that the frequency of a wobble signal is different from the frequency for DVD-RAM after DVD-RAM is set, that no information on the optical disc cannot be reproduced or that no address information is acquired from the optical disc.
Of course, DVDRW is first set and it may be also determined whether an optical disc is DVDRW or DVD-RAM after the similar processing to the above-mentioned one is executed.
In this case, for discrimination between DVD-RAM and DVDRW, the invention provides a disc discriminating method of discriminating DVD-RAM and DVDRW. Further, the invention also provides a disc information reproducing apparatus characterized in that DVD-RAM and DVDRW are discriminated.
The disc discriminating method of discriminating DVD-RAM and DVDRW is based upon the above-mentioned disc discriminating method.
The disc information reproducing apparatus that discriminates DVD-RAM and DVDRW determines whether the corresponding optical disc is DVD-RAM or DVDRW based upon a signal acquired from the optical disc.
The disc information reproducing apparatus is provided with an optical pickup that radiates a laser beam on an optical disc and detects a signal based upon reflected light from the optical disc, an information reproducing circuit (a regenerative signal processing circuit that executes processing for reproducing information acquired from the optical disc, which at least includes a regenerative signal demodulating circuit) that reproduces information recorded on the optical disc based upon the signal detected by the optical pickup, a focus error signal generating circuit that generates a focus error signal based upon the signal detected by the optical pickup, a tracking error signal generating circuit that generates a tracking error signal based upon the signal detected by the optical pickup, a wobble signal extracting circuit that extracts a wobble signal from the signal detected by the optical pickup, an actuator (a focusing actuator and a tracking actuator) that controls the position of a laser beam radiated from the optical pickup, a disc motor that rotates the optical disc, a driving circuit that drives the actuator and the disc motor, a servo control circuit that controls the driving circuit based upon the focus error signal or the tracking error signal and a control circuit that at least controls the information reproducing circuit and the servo control circuit.
A disc information reproducing apparatus that discriminates DVD-RAM and DVDxe2x88x92RW or DVD+RW based upon a tracking error signal acquired from the tracking error signal generating circuit in the above-mentioned configuration is provided.
Or a disc information reproducing apparatus that discriminates DVD-RAM and DVDxe2x88x92RW or DVD+RW based upon a wobble signal acquired from the wobble signal extracting circuit in the above-mentioned configuration is provided.
The above-mentioned information reproducing circuit (the regenerative signal processing circuit that executes processing for reproducing information acquired from an optical disc, which at least includes the regenerative signal demodulating circuit) reproduces information recorded on the optical disc. However, an apparatus that records information on an optical disc is provided with an information recording circuit, the information recording circuit executes processing for recording information on the optical disc and at least includes a recording signal processing circuit and a recording signal modulating circuit.
The above-mentioned optical disc discriminating method is a method of discriminating a disc based upon the amplitude of a tracking error signal, reflected light quantity, reflex time, the number of reflected signals, the amplitude of reflected light by a laser, the frequency of an acquired wobble signal (however, depending upon whether a wobble signal is acquired or not) and whether reproduction is possible under predetermined setting or not, however, the order and the combination of these can be freely set according to the type of the optical disc to be discriminated and a situation of the discrimination. The number of steps for processing for discrimination and time required for discrimination can be also changed by changing the order and the combination. It is also similar in the disc information reproducing apparatus.
The above-mentioned predetermined value is required to be set in consideration of a situation in which the above-mentioned discriminating method is executed. That is, the sensitivity of the optical pickup or the gain of a used amplifier in case the above-mentioned discriminating method is executed can be varied. Therefore, these factors are also required to be considered to set a predetermined value. However, even if there are various factors, a value at which a disc can be discriminated is required to be set as a predetermined value.
Further, only the reproducing apparatus is described above, however, the invention can be also applied to a recording apparatus.